French Involvement with the European Southern Observatory

April 2012

France was a founding member of the European Southern Observatory (ESO) at the time of the signing of the original convention on 5 October 1962 and the membership was ratified by the French Parliament in 1964.

Discoveries by French astronomers using ESO telescopes

R. Pain (LPNHE, CNRS-IN2P3, and University of Paris VI and VII, Paris, France) and A. G. Kim (PCC, CNRS-IN2P3, and Collège de France, Paris, France) are members of one of the teams that discovered the accelerating expansion of the Universe. This work was awarded the Nobel Prize for Physics in 2011, and partly based on data collected on ESO telescopes. [from Perlmutter et al., 1999; Riess et al 98]

Examples of ESO science press releases since 2010 with major involvement from French astronomers or from astronomers working at French institutes:

Planets and Extrasolar planets

eso1144 Lutetia: a Rare Survivor from the Birth of the Earth. New observations indicate that the asteroid Lutetia is a leftover fragment of the same original material that formed the Earth, Venus and Mercury. Astronomers have combined data from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes. They found that the properties of the asteroid closely match those of a rare kind of meteorites found on Earth and thought to have formed in the inner parts of the Solar System. Lutetia must, at some point, have moved out to its current location in the main asteroid belt between Mars and Jupiter.Pierre Vernazza, ESO, Astronomer Philippe Lamy; Laboratoire d'Astrophysique de Marseille, Marseille, France

eso1142 Faraway Eris is Pluto's Twin: Dwarf planet sized up accurately as it blocks light of faint star - Astronomers have accurately measured the diameter of the faraway dwarf planet Eris for the first time by catching it as it passed in front of a faint star. The observations show that Eris is an almost perfect twin of Pluto in size. Eris appears to have a very reflective surface, suggesting that it is uniformly covered in a thin layer of ice, probably a frozen atmosphere. The results were published in the 27 October 2011 issue of the journal Nature.Bruno Sicardy; LESIA-Observatoire de Paris, CNRS, Université Pierre et Marie Curie; Paris, France

eso1015 Triton’s Summer Sky of Methane and Carbon Monoxide. According to the first ever infrared analysis of the atmosphere of Neptune's moon Triton, summer is in full swing in its southern hemisphere. The European observing team used ESO's Very Large Telescope and discovered carbon monoxide and made the first ground-based detection of methane in Triton's thin atmosphere. These observations revealed that the thin atmosphere varies seasonally, thickening when warmed.Emmanuel Lellouch, LESIA, Observatoire de Paris, France

eso1204 Planet Population is Plentiful - Planets around stars are the rule rather than the exception: An international team has used the technique of gravitational microlensing to measure how common planets are in the Milky Way. After a six-year search that surveyed millions of stars, the team concludes that planets around stars are the rule rather than the exception. The results appeared in the journal Nature on 12 January 2012.Arnaud Cassan; Institut d'Astrophysique de Paris; Université Pierre et Marie Curie , Paris, France

eso1024 Exoplanet Caught on the Move. For the first time, astronomers have been able to directly follow the motion of an exoplanet as it moves from one side of its host star to the other. The planet has the smallest orbit so far of all directly imaged exoplanets, lying almost as close to its parent star as Saturn is to the Sun. Scientists believe that it may have formed in a similar way to the giant planets in the Solar System. Because the star is so young, this discovery proves that gas giant planets can form within discs in only a few million years, a short time in cosmic terms.Anne-Marie Lagrange, LAOG, Grenoble, France

eso1011 First Temperate Exoplanet Sized Up. Combining observations from the CoRoT satellite and the ESO HARPS instrument, astronomers have discovered the first “normal” exoplanet that can be studied in great detail. Designated Corot-9b, the planet regularly passes in front of a star similar to the Sun located 1500 light-years away from Earth towards the constellation of Serpens (the Snake).Claire Moutou, Laboratoire d'Astrophysique de Marseille, Marseille, France

Stars

eso1148 - Vampire Star Reveals its Secrets: PIONIER, developed at LAOG/IPAG in Grenoble, France, is a visiting instrument at the Paranal Observatory. PIONIER is funded by Université Joseph Fourier, IPAG, INSU-CNRS (ASHRA-PNPS-PNP) ANR 2G-VLTI and ANR Exozodi. IPAG is part of the Grenoble Observatory (OSUG). Astronomers have obtained the best images ever of a star that has lost most of its material to a vampire companion. By combining the light captured by four telescopes at ESO’s Paranal Observatory they created a virtual telescope 130 metres across with vision 50 times sharper than the NASA/ESA Hubble Space Telescope. Surprisingly, the new results show that the transfer of mass from one star to the other in this double system is gentler than expected.Nicolas Blind and Jean-Baptiste Le Bouquin; IPAG; Grenoble, France

eso1132 The Star That Should Not Exist: A team of European astronomers has used ESO’s Very Large Telescope (VLT) to track down a star in the Milky Way that many thought was impossible. They discovered that this star is composed almost entirely of hydrogen and helium, with only remarkably small amounts of other chemical elements in it. This intriguing composition places it in the “forbidden zone” of a widely accepted theory of star formation, meaning that it should never have come into existence in the first place. The results appeared in the 1 September 2011 issue of the journal Nature.Dr Elisabetta Caffau, Observatoire de Paris, Université Paris Diderot, CNRS, Paris, France, Dr Piercarlo Bonifacio; Observatoire de Paris, Université Paris Diderot, CNRS, Paris, France

eso1121 The Flames of Betelgeuse - New image reveals vast nebula around famous supergiant star Using the VISIR instrument on ESO’s Very Large Telescope (VLT), astronomers have imaged a complex and bright nebula around the supergiant star Betelgeuse in greater detail than ever before. This structure, which resembles flames emanating from the star, is formed as the behemoth sheds its material into space.Pierre Kervella and Guy Perrin, LESIA, Observatoire de Paris / CNRS, Université Pierre et Marie Curie / Université Denis Diderot (Paris 7), Paris, France

eso1110 A Very Cool Pair of Brown Dwarfs - Observations with the European Southern Observatory’s Very Large Telescope, along with two other telescopes, have shown that there is a new candidate for the coldest known star: a brown dwarf in a double system with about the same temperature as a freshly made cup of tea — hot in human terms, but extraordinarily cold for the surface of a star. This object is cool enough to begin crossing the blurred line dividing small cold stars from big hot planets.Philippe Delorme, Institut de planétologie et d’astrophysique de Grenoble, France Christian Veillet, Executive Director, CFHT, Hawaii, USA

eso1028 Black Hole Blows Big Bubble. Combining observations made with ESO’s Very Large Telescope and NASA’s Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery was reported in the journal Nature.Manfred W. Pakull and Christian Motch, University of Strasbourg, Strasbourg, France

Galaxies, distant universe and cosmology

eso1130 Giant Space Blob Glows from Within: VLT finds primordial cloud of hydrogen to be centrally powered. Observations from ESO’s Very Large Telescope have shed light on the power source of a rare vast cloud of glowing gas in the early Universe. The observations show for the first time that this giant “Lyman-alpha blob” — one of the largest single objects known — must be powered by galaxies embedded within it. The results appeared in the 18 August 2011 issue of the journal Nature.Matthew Hayes, University of Toulouse, Toulouse, France

eso1108 The Most Distant Mature Galaxy Cluster: Young, but surprisingly grown-up - Astronomers have used an armada of telescopes on the ground and in space, including the Very Large Telescope at ESO’s Paranal Observatory in Chile to discover and measure the distance to the most remote mature cluster of galaxies yet found. Although this cluster is seen when the Universe was less than one quarter of its current age it looks surprisingly similar to galaxy clusters in the current Universe.Raphael Gobat, Laboratoire AIM-Paris-Saclay, CEA/DSM-CNRS–Université Paris Diderot, Gif-sur-Yvette, France

eso1041 Clearing the Cosmic Fog - The Most Distant Galaxy Ever Measured: A European team of astronomers using ESO’s Very Large Telescope (VLT) has measured the distance to the most remote galaxy so far. By carefully analysing the very faint glow of the galaxy they have found that they are seeing it when the Universe was only about 600 million years old (a redshift of 8.6). These are the first confirmed observations of a galaxy whose light is clearing the opaque hydrogen fog that filled the cosmos at this early time. The results were presented at an online press conference with the scientists on 19 October 2010, and published in the 21 October issue of the journal Nature.Matthew Lehnert, Observatoire de ParisNicole Nesvadba, Institut d'Astrophysique Spatiale

Results from the ESO Top-10 astronomical discoveries

First image of an exoplanet

The VLT has obtained the first-ever image of a planet outside our Solar System. The 5-Jupiter-mass planet orbits a failed star — a brown dwarf — at a distance of 55 times the mean Earth-Sun distance. The paper, lead by French astronomer Gael Chauvin, was published in Science in 2004.Science paper: Chauvin et al. 2004 (Telbib). See also the ESO Press Release eso0428

Cosmic temperature independently measured

The VLT has detected carbon monoxide molecules in a galaxy located almost 11 billion light-years away for the first time, a feat that had remained elusive for 25 years. This has allowed astronomers to obtain the most precise measurement of the cosmic temperature at such a remote epoch. French astronomers Cedric Ledoux (ESO) and Patrick Petitjean (IAP) contributed to this project.Science paper: Srianand, R. et al, 2008, A&A (Telbib). See also the ESO Press Release eso0813

Oldest star known in the Milky Way

Using ESO's VLT, astronomers have measured the age of the oldest star known in our galaxy, the Milky Way. At 13.2 billion years old, the star was born in the earliest era of star formation in the Universe. Uranium has also been detected in a Milky Way star and used as an independent estimate of the age of the galaxy. Profs. Cayrel and Spitte, from Meudon, led one of the projects.Science paper: Pasquini et al. 2004 (Telbib); Cayrel, R et al, 2001, Nature. See also the ESO Press Release eso0425 and the ESO Press Release eso0106

Number of French astronomers and staff working at ESO

As of June 2017 there are 82 French nationals employed at ESO as staff and students. 55 in Garching and 27 in Chile.

France has contributed to many aspects of ESO. In the following sections we list some of the largest contracts placed related to the Atacama Large Millimeter/submillimeter Array (ALMA) on on the Chajnantor plateau in the Chilean Andes, the ESO Very Large Telescope (VLT) on Cerro Paranal and the planned Extremely Large Telescope (ELT) to be built on Cerro Armazones, close to Paranal.